Swift and AVFoundation: Playing audio while animating a label - ios

Question

I have an app that I'm adding sounds to. It has a keypad and when the user taps a button, the number animates to show the user that their press went through.
However, since both are happening on the main thread, adding the following code below, the play() function causes a slight delay in the animation. If the user waits ~2 seconds and taps a keypad number again, they see the delay again. So as long as they're hitting keypad numbers under 2s, they don't see another lag.
I tried wrapping the code below in a DispatchQueue.main.async {} block with no luck.
if let sound = CashSound(rawValue: "buttonPressMelody\(count)"),
let url = Bundle.main.url(forResource: sound.rawValue, withExtension: sound.fileType) {
self.audioPlayer = try? AVAudioPlayer(contentsOf: url)
self.audioPlayer?.prepareToPlay()
self.audioPlayer?.play()
}
How can I play this audio and have the animation run without them interfering and with the audio coinciding with the press?
Thanks

Answer 1

I experienced a rather similar problem in my SwiftUI app, and in my case the solution was in proper resource loading / AVAudioPlayer initialization and preparing.
I use the following function to load audio from disk (inspired by ImageStore class from Apple's Landmarks SwiftUI Tutorial)
final class AudioStore {
typealias Resources = [String:AVAudioPlayer]
fileprivate var audios: Resources = [:]
static var shared = AudioStore()
func audio(with name: String) -> AVAudioPlayer {
let index = guaranteeAudio(for: name)
return audios.values[index]
}
static func loadAudio(with name: String) -> AVAudioPlayer {
guard let url = Bundle.main.url(forResource: name, withExtension: "mp3") else { fatalError("Couldn't find audio \(name).mp3 in main bundle.") }
do { return try AVAudioPlayer(contentsOf: url) }
catch { fatalError("Couldn't load audio \(name).mp3 from main bundle.") }
}
fileprivate func guaranteeAudio(for name: String) -> Resources.Index {
if let index = audios.index(forKey: name) { return index }
audios[name] = AudioStore.loadAudio(with: name)
return audios.index(forKey: name)!
}
}
In the view's init I initialize the player's instance by calling audio(with:) with proper resource name.
In onAppear() I call prepareToPlay() on view's already initialized player with proper optional unwrapping, and finally
I play audio when the gesture fires.
Also, in my case I needed to delay the actual playback by some 0.3 seconds, and for that I despatched it to the global queue. I should stress that the animation with the audio playback was smooth even without dispatching it to the background queue, so I concluded the key was in proper initialization and preparation. To delay the playback, however, you can only utilize the background thread, otherwise you will get the lag.
DispatchQueue.global(qos: .userInitiated).asyncAfter(deadline: .now() + 0.3) {
///your audio.play() analog here
}
Hope that will help some soul out there.